1. Field of the Invention
A non-composite impact-resisting structure fabricated from sheet metal units and reinforcing elements.
2. Description of the Prior Art
Four basic types of impact-resistant wall structures are known in the art.
The customary impact-resistant wall structure -- the reinforced concrete barrier (RCB) -- is fabricated from reinforced concrete monolithic blocks. In the design of an RCB, concrete spalling at its interior face is the governing criterion for establishing the thickness of the RCB for an anticipated impact exposure. Concrete spalling creates hazardous high-velocity secondary missiles. Although the RCB provides the highest impact resistance, it is not only expensive from a materials standpoint, but also is heavy and space-consuming. A typical RCB may weigh 300 pounds per square foot.
A second type of impact-resistant wall -- the stiffened steel plate barrier (SSPB) -- is fabricated from armor-plate steel of substantial thickness. The SSPB is more flexible and undergoes a greater amount of deformation during impact. The SSPB offers lower impact dynamic reaction over a longer period of time. The SSPB is objectionable because of the cost, the weight and the difficulty of installation. A typical SSPB may weigh about 42 pounds per square foot.
Another impact-resistant wall structure -- the composite panel barrier (CPB) -- is known. See, for example, copending application serial number 723,983 filed Sept. 16, 1976 (now U.S. Pat. No. 4,078,350), and assigned to the assignee of the present invention. The CPB is fabricated from inner and outer sheet metal cellular panel units and concrete columns. For higher anticipated impact exposures, reinforcing rods may be embedded in certain or all of the concrete columns. For still higher anticipated impact exposures, reinforcing rods may also be provided in the cells of the outer sheet metal cellular panel units to increase the shear resistance. The CPB is objectionable for use in offshore power stations and in roof structures because of the weight. A typical CPB may weigh about 128 pounds per square foot.
Still another impact-resistant wall structure -- the non-composite panel barrier (NCPB) -- is known which is fabricated from one or more layers of sheet metal cellular units. When two or more layers are utilized, the cells of one layer extend perpendicular to the cells of the adjacent layers. See "Non-Composite and Composite Steel Panels for Tornado Missile Barrier Walls," by Raymond M. L. Ting, appearing in "Second ASCE Specialty Conference on Structural Design of Nuclear Plant Facilities," 1975, published by American Society of Civil Engineers. While the weight per square foot of the NCPB is less than that of each of the above-described barriers, its energy absorption capacity and shear resistance are considerably less than those of the above-described barriers.